1. Field of the Invention
The invention relates to a catheter for delivery of beneficial agents to a target site, and more particularly, the invention relates to a DMSO compatible, flow directed microcatheter for delivery of beneficial agents to a target site in the vasculature.
2. Brief Description of the Related Art
Microcatheters are used to deliver beneficial agents such as diagnostic, therapeutic, or occlusive agents to a target site within the vasculature. When a catheter is to be inserted into the various small blood vessels of the brain, heart, kidneys, etc., which are far away from the catheter insertion point and require passage of the catheter through many twists and turns of the vasculature, microcatheters are used which are able to access these various small blood vessels. Microcatheters may be either tracked with a guidewire to the target site or may be flow directed.
A guidewire directed catheter is provided with a guidewire within the lumen of the catheter to assist in advancing the catheter through the vasculature. Typically, a guidewire and catheter are inserted together into an artery such as the femoral artery and the guidewire and catheter are pushed and twisted to navigate the catheter from the artery to a target site. Once a distal tip of the catheter has been placed at a target site, the guidewire is then removed to allow injection of a beneficial agent through the lumen of the catheter. The process of tracking a catheter to a target site with a guidewire becomes increasing difficult as the guidewire, catheter, and target vessel become very small, particularly, when the target site is deep within the vasculature and involves a highly tortuous path for access.
Accordingly, flow directed catheters may be used when it is necessary to reach a target site deep within the vasculature. One type of flow directed catheter includes a highly flexible catheter having an inflatable, pre-punctured balloon at a distal tip. The balloon is continuously reinflated and carried by blood flow in the vasculature to the target site. The flow directed balloon catheter is extremely flexible at the distal tip to allow the balloon to carry the catheter through the vasculature. The extreme flexibility of the catheter distal tip results in difficulty in advancing the catheter from the proximal end without causing buckling.
Another type of flow directed catheter includes a flexible distal tip which is directed to a target site as a result of the blood flowing to the site. These flow directed catheters must have sufficient columnar strength to allow the catheter to be advanced to the target site by pushing the catheter from a proximal end. Additionally, the flow directed catheter must have a tip which is flexible enough to navigate the tortuous blood vessel pathways while having sufficient pushability to allow the catheter to be advanced, and having sufficient burst strength to withstand injection pressures.
In order to achieve the objectives of flexibility, strength, and pushability, flow directed microcatheters have generally been formed of polyurethane. However, polyurethane is undesirable for the delivery of many beneficial agents including solvents because many solvents will have the tendency to dissolve polyurethane by pulling plasticizers and loose radicals out of the polyurethane.
An example of a beneficial agent including a solvent which is delivered to a target site within the vasculature is a liquid embolic composition used for the treatment of arterial venous malformations (AVMs), tumors, intercranial aneurysms, and the like. One type of liquid embolic composition used for treatment of, e.g., AVMs includes a water soluble biocompatible, non-biodegradable polymer dissolved in a biocompatible solvent. The liquid embolic composition can be used for prevention of bleeding, prevention of blood supply to tumors, as well as for blocking blood flow within aneurysms, and many other uses. As the liquid embolic composition is delivered to the target site via the microcatheter, the solvent dissipates from the polymer material of the liquid embolic composition causing the polymer material within the target site to solidify occluding an AVM, blood vessel, aneurysms, or other vascular abnormality. However, when delivery of the liquid embolic composition is attempted via conventional prior art polyurethane microcatheters, the catheter will swell and/or dissolve during use.
Accordingly, it would be desirable to provide a flow directed catheter with sufficient strength and flexibility to be inserted in a flow directed manner into tortuous paths of the vasculature which is compatible with the delivery of a beneficial agent including a solvent, such DMSO (dimethylsulfoxide). However, many materials which are compatible with various solvents including DMSO have insufficient flexibility and strength for use in the vary small diameter flow directed microcatheters.